Thyroid Pathology Quiz

Papillary carcinoma is the most common type with ~80% of thyroid cancers being papillary. Follicular accounts for ~10%. Medullary accounts for ~5%. Anaplastic is very rare.

Extensive infiltration into the parenchyma is typically seen in Hashimoto's thyroiditis. All other features are typical of Graves disease. In Graves disease IgG TSH-like autoantibodies cause stimulation of the TSH receptor causing hyperplasia of the follicles. These follicles are irregular shape and display scalloping of the colloid.

Medullary carcinoma is the proliferation of parafollicular C cells which produce calcitonin. Calcitonin decreases serum calcium, however it should be noted that this is not a prominent feature in medullary carcinoma.

Anaplastic has a ~20-35% survival at 1 year.
Medullary 50% at 10 years.
Follicular 92% at 10 years.
Papillary 98% at 10 years.

Malignant cells in an amyloid stroma is a typical feature of medullary carcinoma. It is associated with MEN-2 syndrome, local and lymphatic spread and high levels of calcitonin are seen due the proliferation of parafollicular C-cells (which produce calcitonin). Clinically the mass is usually firm and painless. (Ref: Pathoma, Robbins and Cotran)

Dense fibrosis of the thyroid gland is usually seen in Riedel's thyroiditis, a rare form of thyroiditis showing fibrosis of the thyroid, neck structures and sometimes other areas of the body. The clinical picture of sudden onset neck pain radiating to the facial region, including the ears, in a 30-50 year old female following a upper respiratory tract infection indicates subacute thyroiditis, also called de Quervain’s thyroiditis.

A major differentiating feature between follicular carcinoma and follicular adenoma is the carcinomas ability to break through the follicular capsule. This is unable to be distinguished via fine needle aspiration because the needle breaks through the capsule. All other features are descriptive of follicular carcinoma, with approximately 1/3rd having PI-3K/AKT pathway mutations.

‘Orphan Annie eye’ nuclei are pathognomonic for papillary carcinoma. Although clinically a thyroglossal duct cyst is likely, the histology findings indicate papillary carcinoma. (Ref: Cotrans, Pathoma)

Anaplastic carcinomas are highly anaplastic, undifferentiated cells and are usually negative for any markers of thyroid differentiation such as thyroglobulin.

Thyroglossal ducts are cystic dilations of thyroid duct remnant. The thyroid gland embryologically develops at the base of the tongue and then migrates to the anterior neck, a thyroglossal duct cyst may develop at any stage if the duct fails to close.